1. Field of the Invention
The present invention relates to a thin-film magnetic head comprising a perpendicular recording head portion adapted to implement magnetic recording operation in the perpendicular recording mode as well as a head gimbal assembly and a hard disk system comprising that thin-film magnetic head.
2. Explanation of the Prior Art
By the recording mode, a thin-film magnetic head is broken down into a longitudinal recording mode in which information is recorded in a hard disk (recording medium) in its longitudinal direction and a perpendicular recording mode in which data are recorded with the direction of recording magnetization set in the perpendicular direction to the recording plane of the hard disk. Of these, a thin-film magnetic head of the perpendicular recording mode is now considered to be more promising than that of the longitudinal recording mode, because of having the merits of having much higher recording densities and being less likely to be affected by thermal fluctuations.
When the thin-film magnetic head of the perpendicular recording mode is operated to record data in an inner or outer peripheral area of a hard disk that is a recording medium, by the way, the magnetic pole end of a main magnetic pole on an air bearing surface (ABS) side—said main magnetic pole is located on that ABS that is a plane opposed to the recording medium—makes a certain skew angle with the tracks of the hard disk. When the perpendicular magnetic recording head has high write capability, there is a problem or a so-called “blurring on write” in which redundant data get recorded between adjoining tracks by the occurrence of that skew angle. This “blurring on write” has adverse influences on the detection of servo signals, and the S/N ratio of output waveforms. For this reason, a conventional perpendicular magnetic recording head has a main magnetic pole layer with its ABS side-magnetic pole end configured into a trapezoidal shape of width decreasing gradually toward one direction.
A problem with the prior art perpendicular magnetic recording head is, however, that when information is recorded in it at high densities, there is a phenomenon called “pole erasure” in which data already written in the hard disk are erased off. The “pole erasure” refers to the phenomenon in which after data are written in a hard disk having a large maximum coercive force Hc, a leakage magnetic flux flows from the ABS of the magnetic head into the hard disk even without conduction of recording currents through a thin-film coil, with the result that other data are erased off.
The situation being like this, the present invention has been made with a view to providing a thin-film magnetic head of the perpendicular recording mode, which works for reducing the occurrence of pole erasure, and is improved in the stability of recording operation.